The invention relates to a drive unit of a fluid-actuated linear drive, comprising a piston rod, an annular drive piston seated coaxially on the piston rod and a buffer sleeve which is likewise seated coaxially on the piston rod while axially adjoining the drive piston and which is used for end-of-stroke cushioning purposes, these components being secured to one another with the assistance of a welded joint.
The invention further relates to a fluid-actuated linear drive equipped with such a drive unit.
Finally, the invention relates to a method for the manufacture of a drive unit of a fluid-actuated linear drive which comprises a piston rod, an annular drive piston seated coaxially on the piston rod and a buffer sleeve which is likewise seated coaxially on the piston rod while axially adjoining the drive piston and which is used for end-of-stroke cushioning purposes, these components being secured to one another with the assistance of a welded joint.
Such prior art is known from EP 1 503 114 B1, in which an annular drive piston pushed onto a piston rod is axially clamped immovably between two retaining rings which axially flank the drive piston on both sides and are welded to the piston rod by means of a laser weld which is concentric with the piston rod. Alternatively, one end of the drive piston can be supported on a step of the piston rod, so that only the other end is secured by means of a retaining ring welded to the piston rod. A buffer sleeve for end-of-stroke cushioning purposes is pushed onto the piston rod and latched to one of the retaining rings. The buffer sleeve is mounted after the establishment of the welded joint between the retaining ring and the piston rod.
The known drive unit can be produced advantageously, because the axial position of the drive piston relative to the piston rod can be predetermined in a variable manner by the selection of the location of the welded joint. In this way, different customer requirements can be met in an extremely flexible way. It nevertheless involves a not inconsiderable time for the installation of the buffer sleeve, which has to be pushed onto the piston rod after a retaining ring has been welded on and which then has to be latched to the retaining ring.
DE 101 41 560 A1 discloses a fluid-actuated operating cylinder and a method for its manufacture, wherein a piston is pushed onto the piston rod and directly secured to the piston rod by means of a riveted or welded joint. The piston can in particular be secured to the piston rod by friction welding.
DE 40 22 447 A1 discloses a fluid-actuated operating cylinder in which a cylinder end cover is joined to the cylinder barrel by adhesive force in a friction welding process.